EUV Light Source Optical-Path Cover for Debris Isolation
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Solution Overview
Problem
EUV light sources suffer from contamination of optical elements due to debris from target materials like xenon, tin, or lithium, leading to reduced EUV light output, as existing methods using inert gases fail to adequately mitigate debris formation and absorption.
Innovation Solution
A light source apparatus with a design that includes an exhaust case and optical-path covers to separate the exhaust space from the optical path, using purge gas to direct and discharge debris while maintaining a high vacuum state, thereby reducing EUV light absorption and enhancing debris removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If inert gas is introduced near the optical path to mitigate debris, then debris removal is improved, but EUV light is absorbed by the gas and target material vapor, causing contamination of optical elements and reduction in EUV light output
Solution Approach 1:
The patent divides the internal space into distinct regions: an exhaust space containing the target material and purge gas, and an optical path space containing the optical elements. This spatial segmentation prevents the purge gas and target material vapor from the exhaust space from reaching and absorbing EUV light in the optical path space, while still enabling effective debris removal from the target material area.
Solution Approach 2:
The patent extracts the harmful function of the purge gas by directing it exclusively into the exhaust space through the exhaust port, separating its debris removal function from the optical path. The purge gas is taken out of the optical path environment and confined to the exhaust region where it can perform debris removal without interfering with EUV light transmission.
2Object-generated harmful factors
If purge gas is introduced to remove debris from target material, then debris removal is improved, but optical elements become contaminated due to gasified target material
Solution Approach 1:
The patent segments the internal environment into an exhaust space where purge gas and target material vapor coexist, and an optical path space where optical elements are protected. The exhaust port and exhaust channel structure ensure that the purge gas and vapor are confined to the exhaust space and cannot reach the optical elements, thus preventing contamination while maintaining debris removal effectiveness.
Solution Approach 2:
The patent introduces an intermediary structure (exhaust port and exhaust channel) that mediates between the purge gas flow and the optical path. This intermediary confines the purge gas and target material vapor within the exhaust space, acting as a barrier that prevents direct contact with optical elements while still allowing the purge gas to perform its debris removal function.
3Loss of energy
If the optical path is open for EUV light transmission, then EUV light output is maintained, but debris and vapor contaminate optical elements
Solution Approach 1:
The patent maintains an open optical path for EUV light transmission while simultaneously creating a separate exhaust space for debris management. The exhaust port and exhaust channel structure allow the system to have both functions active at the same time without interference, as the purge gas and vapor are confined to the exhaust space while EUV light passes through the optical path.
Solution Approach 2:
The patent applies different environmental conditions to different regions: the exhaust space has high concentration of purge gas and target material vapor for effective debris removal, while the optical path space maintains high vacuum or low gas pressure to prevent contamination and allow EUV light transmission. This local differentiation of environmental quality resolves the contradiction between debris removal and optical element protection.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively maintains EUV light output by minimizing absorption and contamination, improving debris removal efficiency, and preventing optical element contamination.
Implementation Method 1
purge gas is introduced through an intake port formed in the optical-path cover and injected from the one end of the optical-path cover toward the target material, and discharged through the exhaust port via the exhaust space
Implementation Method 2
a collector mirror configured to reflect the generated EUV light
Implementation Method 3
a target material capable of generating EUV light together with plasma when irradiated with laser light
Implementation Method 4
generating EUV light from generated plasma
Implementation Method 5
capable of generating EUV light together with plasma when irradiated with laser light
Implementation Method 6
a filter disposed at the other end of the optical-path cover or inside the optical-path cover, and the filter being configured to let the EUV light pass therethrough
Implementation Method 7
maintaining a high vacuum state, thereby reducing EUV light absorption
Data Source
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AI summary
A light source apparatus (1) according to an embodiment includes: a target material (11) capable of generating EUV light (15) when irradiated with laser light (13); a collector mirror (30) configured to reflect the EUV light (15); an exhaust case (40) including an outer cover (41) disposed between the target material (11) and the collector mirror (30), and an exhaust port (42) communicating with an exhaust space (43) formed on a target material (11) side of the outer cover (41); a cylindrical optical-path cover (50), a diameter of an opening another end (52) being larger than that of an opening at one end (51); and a filter (60) disposed at the other end (52) of the optical-path cover (50) or inside thereof, and configured to let the EUV light (15) pass therethrough, in which purge gas (44) introduced from an intake port (53) formed in the optical-path cover (50) is injected from the one end (51) of the optical-path cover (50) toward the target material (11) and thereby discharged through the exhaust port (42) via the exhaust space (43).